1. Field of the Invention
Internal combustion engines that are used as vehicle motors, stationary motors (generator motors), or for propelling ships as a rule have between 2 and 20 cylinders. In these engines, the bore diameter of the respective cylinders lies within a broad spectrum, sometimes reaching 500 mm in large diesel engines. Depending on the number of cylinders, individually customized fuel injection systems are used, which must be individually tailored to the number of cylinders.
2. Description of the Prior Art
DE 198 37 332 A1 relates to a control unit for controlling the buildup of pressure in a pump unit. The control unit has a control valve with a valve-actuating unit connected to it. The control valve is embodied as an I-valve that opens inward in the flow direction and has a valve body that is supported so that it can slide axially in the housing of the control unit and when the control valve is closed, rests against a valve seat of the control valve from the inside. A throttle device is provided, which throttles the flow through the control valve when the control valve is opened by a small stroke h. When the control valve is opened by this stroke distance, the valve seat is still open, but another valve seat embodied on the control valve is closed so that the medium supplied via the throttle bores flows through the control valve. As a result of such a throttled flow through the control valve, at first a lower pressure is built up in a high-pressure region of the system. When the control valve is completely closed, however, both the first valve seat and the additional valve seat are closed, which interrupts the bypass connection. This causes a high pressure to build up between the pump unit and the low-pressure region of the system, in comparison to the high-pressure region.
DE 42 38 727 A1 relates to a solenoid valve used to control the passageway of a connection between a low-pressure chamber and a high-pressure chamber that is at least sometimes brought to a high fluid pressure, in particular that of a pump working chamber of a fuel injection pump. A valve body is provided, which is inserted into a valve housing and contains a bore in which a valve closing member in the form of a piston can be moved by an electromagnetic counter to the force of a return spring. Starting from a circular, cylindrical circumferential surface, the piston tapers down to a reduced diameter by means of a conical surface; the conical surface cooperates with a conical valve seat, which is disposed on the valve body and connects a high-pressure chamber encompassing the circular cylindrical circumferential surface of the piston to a low pressure chamber encompassing the reduced diameter of the piston. The cone angle of this valve seat is embodied as smaller than the cone angle of conical surface of the piston so that the piston cooperates with the valve seat associated with it by means of a sealing edge produced at the transition between its cylindrical circumferential surface and the conical surface. In the overflow direction from the high-pressure chamber to the low-pressure chamber, the sealing edge has a throttle restriction disposed downstream of it, whose action comes into play at the beginning of the opening stroke. This throttle restriction is formed by means of a throttle passage in the overlap region between the angled surface of the piston and a valve seat surface, in which the angle of the conical surface of the piston is slightly greater, for example 0.5° to 1° greater, than the angle of the valve seat surface so that at the beginning of the opening stroke, the flow cross section between the conical surface of the piston and the valve seat surface decreases steadily over the entire circumference in the overflow direction toward the low-pressure chamber. Because of the high flow speeds of the fuel between the injection phases—whether these be preinjection, main injection, or secondary injection phases—this design cannot completely eliminate cavitation defects.